The present invention relates generally to thin provisioning and tier management and, more particularly, to a method and an apparatus to manage object based tier to improve allocation of media to unallocated area.
In recent years, thin provisioning has become popular. Thin provisioning is a method for allocating area when storage subsystem receives a write command to unallocated area. Currently, a storage subsystem migrates frequently accessed allocated area to fast and expensive media and migrates rarely accessed allocated area to slow and cheap media. However, the storage subsystem cannot determine which media to allocate to unallocated area because the storage subsystem does not have access information for the unallocated area. Therefore, the wrong media may be allocated until the storage subsystem obtains the access frequency.